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April 25, 2015

April 25, 2015

Posted by **Square root** on Tuesday, October 16, 2012 at 8:43pm.

- Math -
**Ms. Sue**, Tuesday, October 16, 2012 at 8:49pmMemorize the common square roots

2 * 2 = 4

3 * 3 = 9

etc.

Then using those squares, you can estimate other square roots.

Example:

square root of 130 =

√ 121 = 11

√ 144 = 12

√ 130 is between 11 and 12

- Math -
**Square root**, Tuesday, October 16, 2012 at 9:20pmOk. Is there an easy way to figure the perfect square root for numbers 13 through 25.

- Math -
**Ms. Sue**, Tuesday, October 16, 2012 at 9:22pm3 * 3 = 9

4 * 4 = 16

5 * 5 = 25

Memorize the squares of 1 - 12

- Math -
**Square root**, Tuesday, October 16, 2012 at 9:32pmSo are u saying to memorize the squares for 13 - 25 as well? Not sure if my question is clear. For e.g. square of 23 is 529. By multiplying the last digit of 23 ( 3x3)= 9, same last digit of the number 529, is there a way I easily work out the first 2 numbers 52?

- Math -
**Reiny**, Tuesday, October 16, 2012 at 9:52pmahh, so you want to square the numbers , not take their square roots

A mental way to multiply any two 2-digit numbers

e.g.

34 x 34

4x4 = 16 , so the last digit is 6 , with 1 to carry

3x4+ 4x3 = 24 plus the one to carry is 25

so the tens digit is 5 , with 2 to carry

3x3 = 9 with 2 to carry is 11

so 34^2 = 1156

the numbers don't have to be the same ...

e.g. 56 x 83

6x3 = 18 , so unit digit is 8 , carry 1

5x3 + 6x8 = 63 , so tens digit is 4 , carry 6

5x8 = 40, plus the carry 6 = 46

56x83 = 4648

but really, am I not just doing the steps of ordinary multiplication ??